DESCRIPTION: The main objective of this proposal is to characterize nociresponsive laminae I and V neurons in the mouse dorsal horn and to address the contribution of key contributors to pain and injury-induced alterations of nociceptive processing. Specifically, we will use in vivo extracellular recordings of these neurons to test the hypothesis that the cloned capsaicin/vanilloid receptor, VR1, is essential for selective modalities of pain sensation and that it contributes to injury-evoked thermal hyperalgesia relayed by neurons originating in both spinal laminae I and V. To specifically address the properties of nociresponsive projection neurons, in some experiments we will antidromically activate laminae I and V projection neurons from parabrachial nucleus and ventral posterior thalamus.